I'm thinking about getting an FPGA board to have a mess around with some 68000 based hardware hacking, does anyone have any suggestions for something fairly cheap which has enough gates to run something like an ST? I was looking at the Spartan-3 with a XC3S400 (http://www.enterpoint.co.uk/store/erol.html#2045X2108) -- is 400k gates enough? I know the old 68000 allegedly had 68k gates, but something tells me the synthisised cores available are likely to be bigger.

MiniMig has the advantage of having a 68k CPU soldered down (freeing up room in the FPGA for the main chipset). It's two main faults are the RAM, there is only 2Mbytes of which (256Kbytes) is used by TOS. The other is it only has 12-bit (4096) colour output (But to be fair, that is better than some FPGA boards!). But it does have an example of a scandoubler (31KHz VGA output stage). It does have VGA connector, Joysticks, mouse, keyboard. It has an example of a floppy disk emulator written in PIC assembler (reads data files from the MMC/SD card and pretends to be a floppy drive).

MiniMig's FPGA is programmed in circuit from a file which is on the SD card. The program on the PIC microcontroller reads the SD card and programs the FPGA on power up. If you want to change anything you recompile, route, copy the file onto the SD card and then power cycle.

Another (sort of) negative of MiniMig is the PIC. Unlike the FPGA it cannot be programmed in circuit. If you want to make any changes to the PIC program you need an external PIC programmer.

What is the PIC used for?

It is an intermediary between the FPGA and the SD card.

It programs the FPGA.

Allows you to select which floppy disk image to "insert"(With an OSD-GUI)

Emulates the floppy disk drive

In the future it will emulate hard disk drives (either using image files, or a DIR)

you can connect just two 220R resisistors in series usualy with B5 and B6 and !mclr pins on any picand at the pin end connect just three wires

and program flash it from icprog.exe even if it has no bootloader over the serial port adding fly programming this way is easy to any existing pic circuit then you just need a serial port rx tx cls wire dtr with dsr in the serial plug and thats it can even be a drag and drop to flash the new file so fly programming is also aok

i toyed with the idea of getting one of these but ill wait a while see what happens myself ... it is nice and looks fab....

The £120 MiniMig cost is still a bit offensive. Especially as you can pick up an XBOX-1 for £20 and run emulators.

Hopefully the MiniMig price could come down with enough sales.

It's a shame, the MiniMig board is just not quite good enough: It's too expensive, the FPGA is a little on the small size (offset with hard 68k), it only has 12-bit colour (Amiga 1200 & Atari Falcon's have 24-bit), and the worst thing it only has 2Mbyte RAM (1.75 usable).

It would be awesome to see an FPGA STE with all the major ports as a proper ST replacement. You could even attach a small LCD and some buttons and make it into a PST I'm not sure it would be worthwhile to emulate anything above a Mega STE though so surely 4MB RAM and 12-bit colour would be fine?

The MiniMig PCB is ideal (if a bit expensive at £120) for reproducing a 1Mbyte Atari ST(e). It's bonus features (over a £10 ST) are 31KHz VGA output, PS2 keyboard and mouse, no floppy drive or disks and it's form factor.

It would take about 1-2 hrs to merge the VHDL Suska sources with the MiniMig PCB VHDL wrapper to get it to working (in the most basic form).

Well if someone was willing to have a crack at that I'd be happy to bug test it.

I have two Minimig bare PCBs left from my run over on amiga.org so I could populate both and send one to the prospective coder willing to take on the task (I'm looking at you alexh ). Of course the programmer could keep the PCB after.

I have a source in China for the parts too, at least the hard to find components.

Incidently, wouldn't you just be able to swap out the two 1mb RAMs for two 2mb chips and update the code? Don't they work like eproms?

Joel wrote:I could populate both and send one to the prospective coder willing to take on the task (I'm looking at you alexh )

Get me a debugged board and I am more than happy to do the work. I was thinking of contacting A-Cube direct.

Joel wrote:Incidently, wouldn't you just be able to swap out the two 1mb RAMs for two 2mb chips and update the code?

I think you would need additional pins on the FPGA between the 68k and SRAM for the extra address line. Exactly how many? Not sure. At least 2 (1 in and 1 out) as the address lines feed through the FPGA.

Can you get 2Mbyte chips?

Last edited by alexh on Sat Feb 23, 2008 10:43 pm, edited 1 time in total.

I wonder what is the state of the Suska code? I am suprised we've not seen Tobiflex port Suska to the TerASIC DE boards. He's done MiniMig and Amstrad CPC. Maybe it's not in as good a state as the archive suggests.

Get me a debugged board and I am more than happy to do the work. I was thinking of contacting A-Cube direct.

Their price is a little over what I'd be paying for components. Plus these have been sitting here a while so better they get put to use than sit there any longer!

You can get up to at least 4mb I'm sure, though might be harder to source. A couple of extra I/O pins on the Xilinx shouldn't be too much of a bind to jumper, though would certainly involve more bug testing

Not sure as to the current state of the Suska core, though Wolfgang seems to think it's capable of running a good chunk of ST software. How accurate that is remains to be seen.

You're saying this from experience? What FPGA platform are you using? Which tool-chain did you use?

Looking at the code there are some "horrible" bits that I am not 100% sure will synthesise (but it could just be the strange coding style). Might have a go tomorrow just a quick go with the Target being the MiniMig FPGA.

It will probably take too long (a few hours) to get real scripts in place and work out the DCM, RAMS and pin-listings etc.

I've been working on average 8 hours a day, 7 days a week since the start of the year on the code, reading and working it out, so I know it quite well now. I think it's quite clear, as good as it can get when keeping the components seperate like the original ST.

stimpy wrote:I've been working on average 8 hours a day, 7 days a week since the start of the year on the code

Don't you have to go to work or something?

If you've been working on it all that time, you must have got something going by now? Lets have a few photo's of it up and running.

I don't think there is any floppy disk emulation included in the current Suska project files. I think it was intended to use real floppy disk drives. That will be the first thing to change once I get a MiniMig board. It should be fairly painless to link into the MiniMig PIC floppy disk emulator.

Where does Wolfgang (Author of Suska) hang out? It would be good to get him here (or us go there) to help forward the project.

alexh wrote:I don't think there is any floppy disk emulation included in the current Suska project files. I think it was intended to use real floppy disk drives. That will be the first thing to change once I get a MiniMig board. It should be fairly painless to link into the MiniMig PIC floppy disk emulator.

The thought is in my head to ditch floppy drive at some point. There are countless ways of doing it, and I think most important is keeping the component count of memory storage devices to as little as possible.

alexh wrote:Where does Wolfgang (Author of Suska) hang out? It would be good to get him here (or us go there) to help forward the project.

Here is a little "artists impression" of what (in my view) an ST replacement should look like. Its not 100% to scale but close enough . All we need now is someone who works in plastics to make such a thing

You do not have the required permissions to view the files attached to this post.